Question

vă rog foarte mult, ajutați mă​

Answer 1

a/2=b/5=c/8=k => a=2k b=5k c=8k
7a+2b-c=80
7•2k+2•5k-8k=80
14k+10k-8k=80
24k-8k=80
16k=80
k= 80/16
k=5 => a=2•5=10
b=5•5=25
c=8•5=40

Answer 2

$\frac{a}{2} = \frac{b}{5} = \frac{c}{8 } = k$

a=2k

b=5k

c=8k

Acum inlocuim:

7×a+2×b-c=80

7×2k+2×5k-8k=80

14k+10k-8k=80

16k=80

k=80÷16

k=5

a=2k

a=2×5

a=10

b=5k

b=5×5

b=25

c=8k

c=8×5

c=40